3 Fuel Pumps in 3 Weeks, Why?

[elliusoopius]

As stated in the title, I have a '95 legacy that has gone through 3 fuel pumps in 3 weeks.

 

I bought the car about a year ago and it's been really reliable until about 3 weeks ago, when my partner parked it after work and the next morning it would just crank over, or start for a few seconds and then sputter and stall. There were no symptoms before he parked it. I diagnosed it as a bad fuel pump and replaced it with one from a '97 legacy that has a bad transmission and has been sitting for a year. The car started up fine and ran until a couple days ago when I was on a hundred or so mile trip. It ran fine until I stopped to get some food, then just wouldn't start, or would start then sputter and stall exactly like before, so I figured it must be the fuel pump since it had been sitting for so long, and replaced it again, this time with a new one from Autozone. Once again, the car started up and ran fine, aside from one little hiccup where I figured there was some air in the fuel line.

 

I got where I was going and moved the car a few times over the weekend, but put almost no miles on it until I was on my way home today. After about 50 or 60 miles I was heading uphill over a mountain pass and pulled over to check something in the back of the car, then when I got back on the road it started to sputter like it wasn't getting gas and I pulled over to the side of the road as the car stalled out. I started it up again and made it about 100' before it started sputtering more and I pulled over again, but this time it recovered without killing the engine and I decided to try to limp it home. Over the next 40 miles it sputtered and lost power a few more times but would recover after a few seconds and I was able to make it home.

 

I'm thinking there's a good possibility that my 3rd pump is gonna eat it soon and I really don't want it to be during my drive to work for the first day of my brand new job on Tuesday, so I'm trying to figure out whats causing these pump problems and hopefully get it sorted tomorrow. I did some googling and couldn't find anyone going through multiple fuel pumps in a legacy like this and I remember reading that they aren't a common item to fail in this car.

 

Here are some things I have done when I was troubleshooting the pump the first time:

 

checked fuel pressure with a gauge before and after the filter, readings were the same, about 10 psi.

 

blew through the fuel filter backwards, some dirty looking stuff came out, but it wasn't difficult at all.

 

checked the wiring to the fuel pump wiring harness and the harness itself with a test light, making sure there was juice for 1-2 seconds when turning the key on.

 

 

 

here are my thoughts on what could be causing it:

 

I just have bad luck and the pump from my other car and the aftermarket one are both shitty.

 

Something contaminating my fuel.

 

electrical problems?

 

 

 

Does anyone have anything to add to these possible causes or suggestions for ways that I can test them or rule them out?

 

Thanks!

[noahrexion]

I think you're on the right track honestly.

 

Has this all happened with the same tank of gas? Where did you fill up at most recently?

Did you happen to run the tank down to empty prior to the first one going?

Have you changed your fuel filter yet (OEM are cheap and worth it)?

Have you tested either of the first two that you pulled with 12V power to see if they run?

What did the pickup look like?

 

Report back!

[doublechaz]

The spec for idle fuel pressure is 29 psi. The spec for heavy load is 37 psi.

 

You could have a bad fuel pressure regulator at the rear end of the passenger side fuel rail letting all the fuel go back to the tank until pressure drops to 10.

 

You could have a wiring problem that isn't sending enough power to the pump. This can mean high resistance somewhere in the system. This could give you full volts when you just check it, but when the circuit is loaded down the voltage is reduced by the resistance. This really stresses electric motors.

 

You can't really count the used pump swap as it probably had about as many miles on it as the one that failed. The ones I've taken apart have brushed motors, so they wear out. What brand of pump did you get from Autozone? I never buy parts there anymore. I once had a car where the starter died after about 14 years. The Autozone starter lasted about 7 months. Back then I *had* a mechanic, and when I told him his response was, "Well, yeah! Of course the Autozone part failed right away."

 

So you may not be able to count the second failure either.

[elliusoopius]

I think you're on the right track honestly.

 

Has this all happened with the same tank of gas? Where did you fill up at most recently?

Did you happen to run the tank down to empty prior to the first one going?

Have you changed your fuel filter yet (OEM are cheap and worth it)?

Have you tested either of the first two that you pulled with 12V power to see if they run?

What did the pickup look like?

 

Report back!

 

No, I've gone through a tank of gas since installing each one and used different gas stations to fuel up too. The first one failed about a day after filling up, the second one failed with about 1/8th of a tank and the third one started acting up right after filling up at a different gas station. The last fill up was at an AMPM in Sacramento, before that I filled up at Maverick in Minden NV and maybe a Safeway in South Lake Tahoe.

 

I haven't changed the filter yet, or tested the old ones. I tossed the second one because I was sleeping in the car for a couple days and didn't want it stinking up the place, but I still have the original, I swapped the whole assembly into the other car so I wouldn't have a big open gas tank hole in there. I should be able to charge up the battery on that car and see if it runs, but if it doesn't how should I hook it up to test it?

 

I'm not sure what you mean by the pickup, but I noticed the screen on the bottom of the first one was pretty dingey looking compared to the one in the other car that I swapped it with the first time.

 

The spec for idle fuel pressure is 29 psi. The spec for heavy load is 37 psi.

 

You could have a bad fuel pressure regulator at the rear end of the passenger side fuel rail letting all the fuel go back to the tank until pressure drops to 10.

 

You could have a wiring problem that isn't sending enough power to the pump. This can mean high resistance somewhere in the system. This could give you full volts when you just check it, but when the circuit is loaded down the voltage is reduced by the resistance. This really stresses electric motors.

 

You can't really count the used pump swap as it probably had about as many miles on it as the one that failed. The ones I've taken apart have brushed motors, so they wear out. What brand of pump did you get from Autozone? I never buy parts there anymore. I once had a car where the starter died after about 14 years. The Autozone starter lasted about 7 months. Back then I *had* a mechanic, and when I told him his response was, "Well, yeah! Of course the Autozone part failed right away."

 

So you may not be able to count the second failure either.

 

I haven't tested the pressure since replacing the first pump. I figured since putting the other pump in made the problem go away then it probably wasn't the pressure regulator. The second time it went out I didn't have a pressure gauge because I was replacing it in the parking lot of a Burger King, so no readings that time, but I stuck my ear on it and it made no noise when the key was turned.

 

The first time I was diagnosing the problem when it wouldn't start, I checked the wiring with an ohmmeter and a test light according to this Youtube video (starting at 4:29):

 

I figured neither of the replacement pumps I used could really be considered reliable, and I am thinking I should just go to Subaru and get one of theirs, but I'm a little apprehensive about putting in a much more expensive one without being fairly confident that I don't have some underlying issue that is going to destroy that one as well.

 

Thanks for your responses, I'm going to attempt to drive to town and get parts later, so we'll see what happens.

Edited May 6, 2019 by elliusoopius

[doublechaz]

I agree about being sure the system is solid before putting in a keeper pump.

 

I'll research if I can find the video from South Main Auto where he does a check on wires under load... ...No luck so far.

Edited May 7, 2019 by doublechaz

[noahrexion]

I meant the strainer which will come with the fuel pump if you buy one.

You should definitely replace the fuel filter when you replace a fuel pump.

Did you get any decent look inside the tank? Has the car been in any accidents/gnarly offroading situation? Any physically damaged lines or anything?

 

I didn't catch the 10psi thing earlier. Does your gauge have a vacuum port on it (giving you the ability to check its accuracy with air)? That is way too low of pressure and it could be blockage (could be as easy as fuel filter literally) or voltage issue as mentioned about (corroded terminals, always suspect grounds first since they're exposed).

 

Do you have a volt meter (not the test light)?

 

The plug to the pump has 6 terminals, when looking straight at it , its oriented:

 

3 - 2 - 1

6 - 5 - 4

 

Terminal 1 is ground and 4 is +12V, you can test the pump that way when its out but don't run it for more than a few seconds without load. And make sure not to make the connection at the pump itself for potential of spark; make your connection away from the fuel ridden pump at the source of power (battery).

[Leggyobw97]

I replaced my fuel pump with the Beck Arnley unit last year and it's been going strong. I second the comments about Autozone parts and the used pump you put in could have also been no good. Try the Beck Arnley one, replace your fuel filter at the same time. Also a good time to do other air/fuel/spark maintenance, like clean your MAF, check/replace filters, check your spark plugs, battery connections... Just while you've got some of that stuff taken apart already. Good luck

[doublechaz]

I never did find that video. Maybe it was one of the other car channels I follow. They can explain it a lot better than I can, but to load test a wire run you are looking for voltage drift at different points along it when it is carrying it's full load. A wire can test good for continuity, but be totally failed in reality. It's like if someone secretly replaced your fire hose with a coffee straw. Continuity says yes, it flows, but you can't actually get enough water through it to put out a fire.

[arlia101]

I agree about being sure the system is solid before putting in a keeper pump.

 

I'll research if I can find the video from South Main Auto where he does a check on wires under load... ...No luck so far.

 

 

Is this the video you were looking for? About diagnosing voltage drop?

 

 

Voltage Drop, Do We Really Need To Know It!?

 

South Main Auto Repair LLC

 

 

 

 

 

 

 

 

 

One of my parents' cars just had this sort of issue, so it's fresh in my mind.

[doublechaz]

That's it. Good work finding it. I looked all through my view history and still couldn't find it.

 

OP, did you end up burning all the time it takes to do this kind of work? Did you find anything?